Electric furnace resistor support



June 6, 1950 A. E. MALM 2,510,507

ELECTRIC FURNACE RESISTOR SUPPORT Filed March 1, 1949 3 Sheets-Sheet 1 fig. .5. g1=iz- 5- Fauna. PM: v- 1 DLMALMA iwezd. MKML June 6, 1950 A. E. MALM ELECTRIC FURNACE RESISTOR SUPPORT Filed March 1, l9

June 6, 1950 A. E. MALM 2,510,507

ELECTRIC FURNACE RESISTOR SUPPORT Filed March 1, 1949 3 Sheets-Sheet 3 JnuLLmibv ivuL Mm Patented June 6, 1950 ELECTRIC FURNACE RESISTOR SUPPORT Anders Evert Malm, Hallstahammar, Sweden, assignor to Aktiebolagct Kanthal, Hallstahammar, Sweden, a corporation of Sweden Application March 1, 1949, Serial No. 79,071 In Sweden March 25), 1946 1 Claim. 1

This invention relates to supports for the resistance wires of electrically heated furnaces, kilns and the like and, more particularly, to a novel ceramic heating wire support element interlockingly cooperable with other similar elements to form a heating wire support unit of any desired length.

In electric ovens, kilns, furnaces, and the like, the heatin wires are supported on a suitable refractory or ceramic material support elements, and these elements are generally arranged along the side walls of the heating chamber. Such mounting is particularly important in high temperature installations, so that the heatin wires or strips are supported in channels in ceramic bricks or blocks.

In order to prevent costly interruptions in heating operations, it is desirable that the heating elements or units be readily interchangeable and replaceable. Such replacement can be effected without too great difliculty when the units are arranged transversely of the floor or roof of the heating chamber. In many installations, such floor or roof mounting is impractical, as when the work to be heated is mounted on cars run through a heating tunnel. In such cases, the aforementioned wall mounting is necessary, with its attendant difliculties in removing, interchanging, or replacing of the heating units.

Where interchangeable heating elements have been used, they have generally comprised a resistance wire wrapped in a helical groove in a cylindrical ceramic rod of relatively large diameter. This arrangement has certain disadvan tages in that the wire particularly if wrapped tightly enough into the groove to assure a close supporting fit at high temperature, has a more or less permanent internal stress which may cause breakage of the wire or cracking of the support. When the wire cools and shrinks, crackin of the support frequently occurs, particularly if pieces of the support lodge in the supporting groove behind the wire when the latter has expanded at high temperatures.

When the ceramic supporting rod is made integral, it has a tendency to crack due to internal stresses resulting from temperature differentials as the heating element is moved into the furnace. As it is impractical to provide a bi-filar winding in the helical support groove, a supply conductor must be brought to each end of the heating element. With large diameter cylindrical heating elements, there is a waste of heat as a good deal of the radiation is directed against the furnace wall rather than onto the work. This considerably increases the temperature of heating element.

In the heating wire support unit of the present invention, the aforementioned difficulties are eliminated by providing a ceramic heating wire support unit comprising a plurality of identical easily disengaged, interlocked wire support units. A support unit of any desired length may be provided by selection of the required number of elements and interfittin the elements to form an elongated support. Due to the use of a number of relatively small elements, rather than a single integral element, the internal stresses in the ceramic, resulting from temperature differentials upon insertion of the unit into the heating chambar, are completely eliminated.

In accordance with the present invention, each individual ceramic wire supporting element is formed essentially as a substantially rectangular block or panel having on its normally vertical forward face a plurality of parallel horizontal shelves in which the heating wire may be supported in a grid like configuration. The rear face of the block is hollowed out, to reduce weight, leaving a reinforcing rib extending around its four sides.

To provide for disengageably interlocking successive elements to form a heating unit of a desired length, the upper end of each element is formed with transversely extending ribs and grooves, and the lower end of each element is formed with transversely extending grooves and ribs arranged to mate, respectively, with the ribs and grooves on the upper end of the element. Thus, two elements can be interlockingly engagedby aligning the grooves and ribs on one end of one element with the mating ribs and grooves on the opposite end of the other element and then effecting transverse relative movement of the elements to interflttingly engage the interlocking formations. The ribs and grooves are so located and related that the interlocked elements are rigidly united and held against any movement except transverse relative movement. When the unit is inserted into its proper position in the heating chamber, wall sections or the latter pre-' vent such lateral movement of the elements.

The support elements may be formed in any desired size, and their forward faces may be arranged to support helical heating wires as well as meander-bent or grid-like heating wires. Due to the arrangement of the wires on the forward face only, all the heat is effectively directed onto the work, so that heating of the support is kept at a minimum.

With the foregoing in mind, it is an object of 3 the present invention to provide a novel heating wire support unit comprising a plurality of disengageable, rigidly interlocked support elements.

Another object is to provide a support element of panel form arranged to support heating wires on its forward face and having interlocking means on one end arranged to mate with interlocking means on the opposite end of an identical support element.

These, and other objects, advantages and novel features of the invention will be apparent from the following description and the accompanying drawings.

In the drawings:

Figs. 1 and 2 are, respectively, vertical and horizontal sectional views of a heating wire support element according to the invention.

Figs. 3 and 4 are, respectively, vertical and horizontal sectional views of an extension member cooperable with the support elements to form a support unit.

Figs. 5 and 6 are, respectively, side elevation and plan views of an end member aranged to be interlocked with the upper end of a support unit form of interlocked support elements and extension members.

Fig. 7 is a vertical sectional view of a furnace showing a heating wire support unit according to the invention, mounted therein.

Fig. 8 is an elevation view, partly in section, taken at right angles to the View in Fig. 7.

Referring to Figs. 1 and 2, the heating wire support element is formed as a substantially rectangular panel having parallel, horizontal wire supporting shelves H on its forward face. Its rear face is hollowed out, to reduce weight, leaving a substantial reinforcing rib extending around its periphery. The side edges have vertical ribs arranged to engage in mating grooves in the heating chamber walls.

To provide for disengageably, rigidly interlocking successive elements to form an elongated support unit, the upper end of the element is formed with a pair of transversely extending ribs l2, l3, and with a groove beneath rib l3. The lower end of the panel is formed with a pair of transversely extending grooves or channels l4, I5, arranged to mate, respectively, with ribs [2, l3, and a rib arranged to mate with the groove in the upper end of the panel. The rear face of the panel has grooves IS in its two horizontal ribs to accommodate the return conductor of the heating wires. Thereby, both ends of the heatin circuit may be advantageously brought to the same end of the assembled heating wire support unit.

The extension member shown in Figs. 3 and 4 has interlocking ribs l2, l3 and interlocking grooves or channels l4, identical with those on the heating panel and identically located. The extension member likewise has grooves IS in its rear surface for the return conductor. The end member of the unit, shown in Figs. 5 and 6, has grooves arranged to interlock with ribs l2, 13 on a heating panel or an extension member, and is formed with a head H. The end member has an aperture'lB for one end 4 of the heating wire and a groove [6 for the return conductor.

Figs. 7 and 8 show the unit as mounted in a furnace, and as including several support elements and extension members rigidly interlocked together and to a supporting end member. The heating wire is shown at [9, and the supply and return conductors at 20 and 2|, respectively. In the illustrated arrangement, the unit is mounted vertically in the furnace.

In eifect, the successive elements are hooked together, and may be replaced or interchanged by withdrawing the unit from the heating chamber and effecting relative transverse movement of successive elements to disengage the interlocking means. It will be understood that the shape and location of the interlocking means may be changed.

While -a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles thereto,

it should be understood that the invention may be otherwise embodied without departing from such principles.

I claim: a

A heating wire support unit comprising a plurality of panels of ceramic material with resistance wire supporting means on their forward faces said panels being arranged in a vertical row and provided with overlapping border sections at their contacting ends, each panel having on one end a pair of transversely extending ribs formed and located to mate with transversely extending grooves arranged on the other end of each panel, the said pair of ribs forming two arms of a half cross, one rib extending in a longitudinal direction from the edge of one panel into a groove in the contacting edge of the.

adjacent panel, and the other rib extending from one overlapping border section perpendicularly thereto into a groove in the overlapped section of the adjacent panel.

ANDERS EVERT MALM.

REFERENCES CITED The following references are of record in the file of thispatent:

UNITED STATES PATENTS Number Name Date 274,354 McCarthy et al. Mar. 20, 1883 1,057,745 Kohn Apr. 1', 1913 1,297,960 Yourtee Mar. 18, 1919 1,472,137 Reid Oct. 50, 1923 1,495,503 Armstrong May 27, 1924 1,535,547 Reid Apr. 28, 1925 1,673,543 Wirz June 12, 1928 1,695,874 Woodson Dec. 18, 1928 1,695,882 Colby Dec. 18, 1928 2,035,306 Fannin Mar. 24, 1936 2,202,874 Smalley June 4, 1940 FOREIGN PATENTS Number Country Date 71,983 Norway Apr. 21, 1947 270,035 Great Britain May 5, 1927 590,675 Great Britain July 24, 1947 648,331 France Aug. 13, 1928 

